Recycling of paper is taking on increasing importance as demands on resources increase. One of the aspects of recycling that is particularly challenging is the area of deinking. Various aspects of deinking are described in the literature. See, for example, L. D. Ferguson, "Deinking Chemistry: Part 1" TAPPI Journal, pages 75-83 (July 1992), and "Deinking Chemistry: Part 2" TAPPI Journal, pages 49-58 (August 1992); B. R. Read, "The Chemistry of Flotation Deinking", TAPPI Proceedings, 1991 Pulping Conference, pages 851-856; J. Jossinet, "Custom Deinking of Newsprint", 77th Annual Meeting Technical Section Canadian Pulp & Paper Association, pages 369-372 (1991); L. D. Ferguson, "The Role of Pulper Chemistry in Deinking" TAPPI Proceedings, 1991 Pulping conference, pages 793-799; T. W. Woodward, "Appropriate Chemical Additives Are Key to Improved Deinking Operations", Pulp & Paper, pages 59-63 (November, 1986); and T. W. Woodward, "Deinking Chemistry", 1991 Chemical Processing Aids Short Course, pages 85-105. Washing deinking and flotation deinking are the two major types of deinking processes. Some preference is given to flotation deinking because it uses less water.
Various approaches have been tried to improve flotation processes for oil-based inks. These approaches have included searching for chemicals that give improved results traditionally, fatty acid or soap have been used as collectors for flotation deinking. However, these chemicals have to be used in large dosages and cause deposit problems, (due to the residue of fatty acid) at the downstream of papermaking process. A variety of chemicals have been tried to obtain improved performance in the deinking process they have had mixed results. Many nonionic surfactants have been used, including alkoxylates of fatty acids, long chain alcohols, and even some fatty oil or natural fat.
Thus, an object of the present invention is to provide an improved process for deinking pulp which comes from sources containing oil-based ink. It is a further object of this invention to provide a deinking process which gives improved results with flotation. These and other objects of the invention will be apparent from the following description.